Device for supplying air to a double surface-aerodynamic-profile

ABSTRACT

A flexible, hollow, lift-developing airfoil has a frontal air inlet, and a valveless air-filled chamber between upper and lower surfaces. The upper surface is impermeable to air. The lower surface has a permeable section which permits air to freely flow therethrough in either direction depending on differential atmospheric pressure inside and outside the chamber. When the airfoil is in horizontally advancing flight, the permeable section is not exposed to the relative wind. Under such conditions air enters the chamber through the frontal opening, and excite through the permeable section. When the airfoil is descending in a substantially vertical direction, the permeable section is exposed to relative wind, and air enters the chamber therethrough, flowing out through the frontal opening, to automatically maintain a desired aerodynamic profile.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a device for supplying air to adouble-surface-aerodynamic-profile, and typically a paraglider or aparachute. More specifically, the device according to the invention isintended to permit the supply of air to the space situated between thelower surface and the upper surface of a parachute or of a paraglider.

2. Description of the Prior Art

Traditionally, this air supply is effected by an open space, provided atthe front of the paraglider, and typically representing between 1 and20% of the total surface area of the lower surface. This air supplybetween lower surface and upper surface is intended to permit theadvance of the paraglider or of the parachute in a plane other than thepurely vertical plane of the to gravity.

Paragliders are currently known which possess at the location of theirforward zone, an a-jour fabric of "mosquito net" type, but theventilation aperture surface area of which never exceeds 20% of thetotal surface area of the lower surface. Now, this supply zone exhibitsa surface area which is insufficient under certain flight conditions.Moreover, this zone is partially or entirely blocked when the whole orpart of the front of the appliance, i.e. paraglider or parachute,becomes folded, for example on account of aerological turbulences.Moreover, this forward zone is in some instances poorly ventilated alongthe direction which is adopted by the appliance, and the aerodynamicprofile of the paraglider is then no longer ensured correctly, leadingin certain instances to a significant fall of the appliance.

In the document EP-A-0,336,277, a paraglider has been proposed, thelower surface of which is equipped with a flap valve which is liable togive rise to pressure variations at the location of the space situatedbetween the lower surface and the upper surface. Nevertheless, thissystem incorporating a flap valve does not permit the maintenance of acorrect aerodynamic profile of the appliance. In fact, it generates atthe location of the sail of the paraglider local variations of pressurewhich are unsuited to slight, as these may give rise to the folding ofthe sail. Moreover, when using such a system it has been possible toobserve phenomena of autorotation, generally leading to the falling ofthe appliance.

SUMMARY OF THE INVENTION

The present invention aims at alleviating these various disadvantages.It relates to a safety device for supplying air to adouble-surface-aerodynamic-profile. This device is characterized in thatthe lower surface area or lower surface is permeable to air over atleast a part of its surface area.

Typically, the lower surface may be permeable to air over the whole orpart of its surface area, depending upon the ultimate intended purposeof the appliance. Accordingly, this lower surface is pierced withorifices, the surface area of which is within the range between 0.001mm² and 4 mm². In fact, it has been noted that if the surface area ofthese orifices were less than 0.001 mm², the lower surface no longerexhibited sufficient permeability to air for the desired effect, andespecially the effect of stabilization of the aero-dynamic-profile ofthe appliance and of advance of the appliance in a plane other thanvertical or subvertical. On the other hand, if the surface area of theorifices of the lower surface is greater than 4 mm², the liftingfunction of the lower surface is no longer ensured and, furthermore, theresultant advance of the appliance cannot take place under correctconditions.

In a particular embodiment of the invention, the lower surface is formedby a free air inlet situated at the location of the forward zone of theappliance, which zone is followed by a zone constructed of a fabricimpermeable to air, similar to the upper surface, and finally a partreferred to as "ventilated", that is to say permeable to air, in a zonewhich is to the rear in relation tot he aerodynamic-profile. Thisparticular feature is more particularly intended to promote the advancein a horizontal or subhorizontal plane of the appliance.

BRIEF DESCRIPTION OF THE DRAWINGS

The manner in which the invention may be implemented and the advantageswhich arise therefrom will emerge more clearly from the illustrativeembodiments which follow, which are given on an indicative butnonlimiting basis, in support of the accompanying figures.

FIG. 1 shows a diagrammatic cross-sectional view of the device accordingto an embodiment of the invention.

FIG. 2 shows a diagrammatic cross-sectional view of another embodimentof the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

As can be seen in FIG. 1, in which a diagrammatic cross-sectional viewof a paraglider has been shown, the latter essentially comprises anupper surface (1) constituting the upper sail and constructed of amaterial impermeable to air, typically a coated fabric, and a lowersurface (2) constituting the lower sail and permeable to air over itsentire surface area. The upper surface and the lower surface (1) and (2)delimit the chord (3) of the aerodynamic-profile.

As has already been stated, the lower surface (2) is permeable to air.It is typically constructed of a woven or bonded material, and isequipped with orifices, the surface area of which is, for example, equalto one square millimeter.

In another embodiment shown in FIG. 2, the upper surface (1) is similarto that of FIG. 1, On the other hand, the lower surface is formed of twoparts, respectively a first part (5), constructed of a fabricimpermeable to air and situated in the vicinity of the central band ofthe paraglider, and, at the rear of said central band, a ventilated part(6) permeable to air and constituting the caudal part of the lowersurface of the paraglider. At the rear end of this caudal part, thelower surface is made integral with the upper surface. As in thepreceding case, it delimits the chord (3) of the aerodynamic-profile.Irrespective of the configuration of the lower surface (2), the surfacearea of the ventilated zone (6) is in all cases greater than 20% of itstotal surface area.

The forward part of the paraglider is constituted by a free inlet (4),permitting the air to be caught without any resistance between the lowersurface and the upper surface.

FIG. 2 shows the straps (7, 8) for fixing to the harness, permitting theparaglider to be attached to the user.

In this manner, appliances are obtained, both parachutes andparagliders, the stability of the aerodynamic-profile of which isstrengthened, and which are capable of ensuring an advance in a planeother than the vertical plane, this advance being favored in relation tothe paragliders and parachutes which are known at the present time.Furthermore, depending upon the ultimate intended purpose of theappliance, it may be the intention to use textiles which are morepermeable to air in one direction than in the other for the lowersurface, for example PORCHER (registered trademark) textiles.

The mounting of this type of lower surface on a sail is conventional anddoes not require any specific implementation.

Such a device is particularly suitable for the construction ofparagliders and parachutes, and it permits a very significant increasein safety in the course of their use, since, as a result of itsstructure, it induces an opening and an inflation of the sail, evenwhere by accident the latter closes. Moreover, in the event of severeturbulences, on account of a relatively uniform distribution of thepressure, and of its self-regulation, the appliance responds in itsentirety to the various air currents, without generating any folding orclosure of the sail, thus emphasizing the safety character for suchparagliders or parachutes.

I claim:
 1. A flexible lift-developing airfoil having an air inlet in afront portion thereof, and further having an upper surface and a lowersurface, and a valveless air-filled chamber therebetween, said lowersurface being permeable to air over at least an appreciable part of itssurface area, said lower surface further being exposed to air in saidchamber at all times during flight, and permitting air to freely exitsaid chamber therethrough when air pressure inside said chamber exceedsair pressure outside said chamber during flight, said upper surfacebeing impermeable to air, said permeable part of said lower surfaceoperatively disposed so as to be substantially unexposed to relativewind force when said airfoil is in horizontally advancing flight, and tobe exposed in relative wind force when said airfoil is descending in asubstantially vertical direction, whereby the airfoil maintains anadvantageous aerodynamic profile and does not autorotate during flight.2. The device of claim 1, wherein said lower surface is permeable to airover its entire surface area.
 3. The device of claim 1, wherein a partof a central zone of said lower surface is impermeable to air, and apart of a caudal zone of said lower surface is ventilated and permeableto air.
 4. The device of claim 1, wherein said permeable portion of saidlower surface comprises a fabric that is pierced with a plurality oforifices, said orifices each having a surface area in a range of 0.001to 4.0 square millimeters.
 5. The device of claim 1, wherein saidpermeable portion of said lower surface comprises more than 20% of thesurface area of said lower surface.
 6. The device of claim 1, whereinsaid device is a paraglider.
 7. The device of claim 1, wherein saiddevice is a parachute.